B737-300 loses cabin pressure. Descends; diverts and lands.

Attributes
ACN	746699
Time
Date	200707
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	msl single value : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zzz.artcc tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 114
ASRS Report	746699
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : cabin alt wiing other flight crewa
Resolutory Action	controller : issued new clearance controller : provided flight assist flight crew : declared emergency
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

We were cruising at FL350 when the cabin altitude warning horn went off. We both looked at the pressure. Cabin was at 10000 ft. We immediately put on our oxygen masks. We then requested a lower altitude from center. Center cleared us to FL300 then on to FL270. I then declared an emergency; and informed center we were going to 10000 ft. Center asked what airport we needed to go to. I advised ZZZ was our diversion city. At the same time I pulled QRH out. Still could not maintain pressure with QRH options. Cabin masks did not deploy. We reached 10000 ft uneventfully where we stayed until switching to ZZZ approach. We briefed flight attendants and passenger on event once reaching 10000 ft. We made an overweight landing at 116200 pounds. Smooth landing with little to normal braking. Taxied to gate and gave aircraft to maintenance.

Original NASA ASRS Text

Title: B737-300 LOSES CABIN PRESSURE. DESCENDS; DIVERTS AND LANDS.

Narrative: WE WERE CRUISING AT FL350 WHEN THE CABIN ALT WARNING HORN WENT OFF. WE BOTH LOOKED AT THE PRESSURE. CABIN WAS AT 10000 FT. WE IMMEDIATELY PUT ON OUR OXYGEN MASKS. WE THEN REQUESTED A LOWER ALT FROM CTR. CTR CLRED US TO FL300 THEN ON TO FL270. I THEN DECLARED AN EMER; AND INFORMED CTR WE WERE GOING TO 10000 FT. CTR ASKED WHAT ARPT WE NEEDED TO GO TO. I ADVISED ZZZ WAS OUR DIVERSION CITY. AT THE SAME TIME I PULLED QRH OUT. STILL COULD NOT MAINTAIN PRESSURE WITH QRH OPTIONS. CABIN MASKS DID NOT DEPLOY. WE REACHED 10000 FT UNEVENTFULLY WHERE WE STAYED UNTIL SWITCHING TO ZZZ APCH. WE BRIEFED FLT ATTENDANTS AND PAX ON EVENT ONCE REACHING 10000 FT. WE MADE AN OVERWT LNDG AT 116200 LBS. SMOOTH LNDG WITH LITTLE TO NORMAL BRAKING. TAXIED TO GATE AND GAVE ACFT TO MAINT.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.